Vibration isolators are used, for example, in motor vehicles. An exhaust manifold is fastened to the upper end of the engine of a motor vehicle, which exhaust manifold comprises a plurality of manifold pipes (in accordance with the number of cylinders) which are typically flanged to the engine block substantially horizontally and then extend in the engine compartment in the downward direction in a bent away manner. The individual manifold pipes are brought together at the lower end of the exhaust manifold. Depending on the type of design, an exhaust gas catalytic converter can be provided so as to adjoin the exhaust manifold directly, which exhaust gas catalytic converter is connected fixedly to the exhaust manifold, for example by a flanged connection. The exhaust system (muffler, pipe) then adjoins the exhaust manifold or the exhaust gas catalytic converter, in which exhaust system the exhaust pipe initially extends bent into the horizontal direction again and is then guided along the underbody of the vehicle.
During operation of a motor vehicle, very considerable vibrations are sometimes produced in the engine. As far as possible, these vibrations are not to be transmitted to the exhaust system, or to as small an extent as possible, for which reason vibration isolators have already been proposed in the literature.
A vibration isolator of this type is described, for example, in JP-A-2000/297638. In this document, an exhaust gas catalytic converter is flanged on at the lower end of the exhaust manifold. An L-shaped plate is fastened by its limb to the engine block, while the exhaust gas catalytic converter is fastened to the protruding foot of the L-shaped plate with the aid of a threaded nut connection. As there are still very high temperatures in this region, the exhaust manifold and optionally the housing of the exhaust gas catalytic converter expand in the downward direction, after a cold start, until the operating temperature is reached. This thermal expansion downward is made possible by a sliding bush which is arranged around the screw and is guided through the foot of the L-shaped plate.
Other types of vibration isolators operate with two mounting plates, of which the first mounting plate is fastened, for example, to the engine block and the second mounting plate is fastened, for example, to the exhaust manifold or to the exhaust gas catalytic converter. The mounting plates are connected to one another with the aid of wire cable pieces. The wire cable pieces extend in the manner of a loop between the mounting plates, that is to say they emerge from the lateral faces of the first mounting plate, are guided in the manner of a loop to the second mounting plate and enter a lateral face of the second mounting plate which stands perpendicularly with respect to the lateral face of the first mounting plate, from which the wire cable pieces emerge. The ends of the wire cable pieces are connected to the respective mounting plate. Vibration isolators of this type are known, for example, from JP-A-2001/290389 or from EP-A-1 138 974.
Suspension means for components of exhaust systems are known from U.S. Pat. No. 3,746,127 and U.S. Pat. No. 2,267,431. In particular, these suspension means also comprise wire cable pieces, the ends of which can be pressed in each case into a sleeve which is then connected to a mounting plate. However, the wire cable pieces have to have a not inconsiderable flexibility in the axial direction, as they have to be capable of absorbing vibrations of the exhaust system, which vibrations occur during driving operation, for example when driving over a ridge in the ground. A very high rigidity of the wire cable piece in the axial direction is therefore undesirable.
A vibration absorber or shock absorber is known from U.S. Pat. No. 5,690,322, without specification of a particular intended use. Although the vibration or shock absorber described in this document likewise comprises a wire cable piece, the ends of which can be pressed into a sleeve, the wire cable piece has a bulge, in order to have sufficient flexibility in the axial direction, in order for it to be possible to be pressed together and pulled apart in the event of an appropriate vibration in the axial direction.